There are currently available several systems for recording sound in a personal computer. Some such devices internally digitize the sound and read it, under control of built-in control circuitry including oscillators, into the bi-directional serial port of a Macintosh microcomputer. This device cannot be used with IBM and compatible PCs that do not have the bidirectional serial port capable of sufficient performance for high quality voice digitizing. Other types of sound digitizing devices employ a circuit board that is put into an available slot within a personal computer; these systems then accept a microphone input at the computer connector for that port. These systems require that the user be technically capable of opening the computer and inserting the board into the slot, and also require that the computer have the right type of slot available. Accordingly, these devices decrease the number of other functional boards that may be plugged into the computer. Further, they cannot be used with laptop and notebook computers that do not have such internal slots.
Other sound digitization systems employ a large external free standing device that accepts a microphone input. The device has the internal oscillators and controls necessary to allow it to sample the input signal and digitize it with a parallel analog to digital (A/D) converter. The parallel data is decomposed into groups of four bits for reading into the computer through four available input pins in the parallel printer port. This system requires the user to supply a separate microphone, is large and cumbersome, complex and costly. Further, having the oscillator in the same enclosure with the sound signal processing circuitry contributes to signal noise, degrading sound quality.